For those who whine about people, who whine about stolen builds: Yes, you could play on singleplayer to stop people sstealing it. But CTFs and TDMs are a bit lame to play alone no? Also people don't want their builds stolen for a reason. Here's an example:
You've just finished your big CTF map and you're ready to test it. People start joining and everyone is having a good time. Then one of the players saves without permission, leaves, starts his own CTF with the same map and claims it's his. So basicly, you worked on the map for days, while this random guy just joins and saves the build, which takes about 15 minutes...Now, nobody has a reason to join your server, when they can just join the other one (where naturalyy it's ok to save the bricks, so soon everyone has the map).